1. Field of the Invention
The invention relates generally to an anchoring system and an associated surgical instrument, which may have multiple uses in orthopaedic surgery such as joint stabilization, bunion correction, ligament reconstruction and similar procedures. More particularly, the anchoring system of the invention may include a system for anchoring two or more body parts together and a system for aligning movement of one anchored body parts relative to another.
2. Related Art
Various devices and methods have been used in the prior art for bone realignment, fixation of the bones or bone portions, and ligament reconstruction repair in order to correct for various orthopaedic conditions, such as hallux valgus, tarsometatarsal sprains, ankle ligament reconstruction, and spring ligament repair.
Hallux valgus is a common foot disorder of several etiologies, which can lead to significant foot pain and deformity. Hallux valgus may be defined as a static subluxation of the first metatarsophalangeal (MTP) joint with lateral deviation of the great toe and medial deviation of the first metatarsal. Moreover, the condition may be accompanied by rotational pronation of the great toe in severe cases. The skeletal deformity results in increased sensitivity to any pressure created by contact. The condition may be self-perpetuating because the pressure that the bunion creates against the patient's footwear causes the metatarsal bone at the point of contact to thicken. A direct result of the thickening of the head of the metatarsal increases the size of the resulting bunion, which increases the severity of the condition and patient discomfort associated with the condition.
One of the most common causes of hallux valgus is prolonged deformation of the foot caused by wearing shoes that do not fit properly, such as high-heeled shoes and narrowly pointed toe shoes. Here, the big toe is forced into an abnormal orientation for a long period of time, which eventually stretches out the joint capsule and promotes abnormal migration of the muscles. There are other factors that may contribute to hallux valgus, which include rounded unstable MTP joint surfaces and oblique joint surfaces located at the proximal first metatarsal joint.
The initial symptom of hallux valgus may be pain at the joint prominence when wearing certain shoes. The capsule may be tender at any stage. Later symptoms may include a painful warm, red, cystic, movable fluctuant swelling located medially and swelling and mild inflammation affecting the entire joint which is more circumferential.
The diagnosis of a hallux valgus condition may include accurately defining a number of critical measurements through the use of x-rays taken of the foot's bone structure. First, the intermetatarsal angle (IM angle) may be determined. The IM angle may be defined by the relationship of the first metatarsal shaft compared to the line of the second metatarsal shaft. Under normal conditions, the IM angle may be in the range of about 6 degrees to about 9 degrees. Secondly, the hallux valgus angle (HV angle), which may be defined by the angle of the line created at the MTP joint between the first metatarsal bone shaft and the first phalangeal bone shaft may be determined. Under normal conditions, the HV angle may in the range of about 9 degrees to 10 degrees. The HV angle may be considered to be in the abnormal range if the measurements are greater than about 15 degrees. Finally, the condition of the MTP joint may be evaluated to determine whether there has been a lateral subluxation of the joint. The combined evaluation of these and other factors will determine the course of action to be taken.
There are numerous types of surgical procedures that may be employed to correct a bunion. Currently, the state of the art consists of various osteotomies to realign the first metatarsal (MT) and the first MTP joint. These procedures do not function through the axis of deformity. Rather, they attempt to realign the bone and joint by translating and rotating the MT through a location that is accessible and minimizes complications. However, there are several complications related to altering blood supply of the MT, and to altering the length and position of the MT associated with this surgical procedure. Furthermore, the surgical exposure required, the trauma to and shortening of the bone from sawing, and the prolonged healing time required all lead to less than satisfactory results.
One alternative to using an osteotomy to treat hallux valgus is to perform a corrective arthrodesis of the tarsometatarsal joint. The advantage of this approach is that the deformity is corrected where it is occurring, and allows for a powerful correction of large deformities. The disadvantage, however, to this approach is that a normal joint is being sacrificed, which alters the subsequent biomechanics of the foot. Additionally, the surgical technique has been found to have a high rate of complications including a high rate of not healing properly.